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DUST COLLECTING SYSTEM FOR COAL CLEANERS Filed May 25, 1927 Patented May26 1931 UNITED STATES PATENT OFFICE JRAY W. ARMS, OF CHICAGO, ILLINOIS;ASSIGNOR 'I'O ROBERTS AND SCHAEFER COM- I PANY, OF CHICAGO, ILLINOIS, -ACORPORATION OF ILLINOIS i DUST COLLECTING SYSTEM FOR COAL CLEANERSApplication filed May 23, 1927. Serial No. 193,468.

I time to time throughout the specification and claims.

My invention is illustrated moreor less diagrammatically in theaccompanying drawings, wherein .Figure 1 is a side elevation of anapparatus embodying my invention;

Figure 2 is an end elevation;

vLike parts are indicated by like characters throughout thespecification and drawings.

VA is an air pervious. material separating deck. It is reciprocated by apulley A driving a crank A; and a link A A is a feed shelf reciprocatingwith the deck adapted to receive coal or other material to be treatedwhich is discharged thereupon through a' spout A from a hopper A. A A Aare material discharge chutes which collect, and

discharge the separated material from the 5 table or deck.

B is a blower driven by a motor 13 and discharging air under pressure]through the chimney B to the underside of the pervious 13 is adust'hoodlocated, above'the deck.

deck. B is a bellows of flexible or other suitable fabric extending downfrom the lower edge of the hood to the deck. This bellows extends downto the deck throughout the major portion of its periphery only so muchof the space betweenthe hooda'nd the deckbeing open as is necessary topermit the atten-dantto inspect the operationof the machine. B isflafunnel formingpar't of the hood B discharging into a pipe B which pipeleads to any suitable dust collecting and separating apparatus; Thisfunnel is located over the feed corner- 0f the table or deck, thatis-,that part of the table or deck where the major portion of the dustoriginates. The dust separator since its'details form no part of theinvention is onlyshown diagrammatically as at B Extending from the dusthood B is an air recirculation pipe C. It discharges into a dusttrap Cand .a pipe C leads therefrom to the intake side of the fan B. C is aconveyor adapted to carry off the dust brought down from the air by thedust trap or settling chamber C C3 is an adjustable make up airsupplyleading to theintake of the fan The necessity of this is caused bythe fact that part of the air taken fromthe hood B is carried off to thedust separator and part of .it

I comes backto the fan or blower. Some of the 7 make up a1r comes inbetween the hood l3 and the deck and the adjustable make up' openingwill be so set and controlled either manually or automatically that.there will always be an inflow of air between the hood.

"and the deck and never an outflow. The re sult of this is that no dustladen air gets out into the room or house in which the table isoperating. The tendency of air flow is al- Ways inward in the entiresystem except that partof. it leading from the blower to the undersidedeck which is above atmospheric pressure. Thus there is no tendency fordust to escape anywhere fromthe system into the room.

Except in connection with the Very finest screens the presence of dustin the recirculated air and therefore in the air blown up through thescreen or pervious deck to float and assist in separating the material,is not a detriment but an advantage because it is understood that inconnection with dust separating the flowing stream of finely divide-dmaterial travels along a separating table under the influence ofgravity, the reciprocation of the table and the floating effect of theair. Experience shows that if anything can bedone to increase thespecific gravity of the air orgas stream the material can be floated"with a decreased velocity, pressureand volume of air. The presence ofdust then in the it does the specific gravity of the air, helps ratherthan hinders in the separating operation.

Experience shows that there is a satura tion point at which the airstream will carry no further dust. Beyond that point dust may bedeposited out in the dust trap or may be screened out by the bed oftraveling material to be treated.

Only that relatively small proportion of the air having the maximumamount of dust is drawn out through the funnel and discharged to aseparate dustcollector. Thus a relatively small dust collector can beused and a high degree of elliciency in dust collection can be obtained.It will not be suiiicient, of course, to try to recirculate all the airbecause under these conditions pressure variations would set up and itwould be quite impossible to keep a suction on the system and on thespace between the hood and the deck and under such conditions air anddust would escape in undesirable quantities into the room and al o heavyparticles which are frequently entrained by the air to the dustseparator might if they were allowed to work back th 'ough the screeningsystem clog the system.

Vhile I have shown part of the air taken from the hood and dischargedthrough a dust separator, it is obydous that suchair may be dischargedinto any suitable system and the dust separator needs not to be of anyparticular type and might take any number of different forms and in factit is conceivable that many things might be done to the air before itreaches the dust separator or it might merely be discharged away fromthe system. 7

One of the important reasons for taking some of the air from the hood.and discharging it either to a separator or hood is that by doing thisit becomes possible to keep all the air except that portion below thedeck under sub-atmospheric pressure so that all leaks except in thatrelatively small part of the system which is under a pressure aboveatmospheric will be in, instead of out, and there will be no tendencyfor dust laden air to escape from the system into the room or housewhere the system is located.

I claim:

1. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a hood overlyingthe entire working area of the table, means for withdrawing air from thehood, and discharging it to the intake side of the blower forrecirculation through the system, meansfor withdrawing from the systemsome of the air from the hood, the system being closed except betweenthe hood and the table whereby air to replace that withdrawn from thesystem must enter the system inwardly across the sides of the table.

2. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a dust separatorand means for conducting to the separator and withdrawing from thesystem that portion of the spent air containing the largest proportionof dust and means for conducting the remainder of the spent air back tothe intake side of the blower for recirculation through the system.

3. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a dust separatorand means for conducting to the separator and withdrawing from thesystem that portion of the spent air containing the largest proportionof dust and means for conducting the remainder of the spent air back tothe intake side of the blower for recirculation through the system, andmeans for discharging into the system across the sides of the table acurrent of make-up air.

4. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a dust separatorand means for conducting to the separator and withdrawing from thesystem that portion of the spent air containing the largest proportionof dust and means for conducting the remainder of the spent air back tothe intake side of the blower for recirculation through the system, andmeans for discharging into the system across the sides of the table acurrent of make-up air, and controllable means associated with theblower for adding additionalmake-upair thereto.

'5. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a dust separatorand means for conducting to the separator and withdrawing from thesystem that port-ion of the spent air containing the largest proportionof dust and means for conducting the remainder of the spent air back tothe intake side of the blower for recirculation through the system, anda dust trap through which the air passeson its return to the blower.

6. In an air cleaning system, a pneumatic stratifying table, a bloweradapted to discharge air under pressure therethrough, a dust separatorand means for conducting to the separator and withdrawing from thesystem that portion of the spent air containing the largest proportionof dust and means for conductingthe remainder of the spent air back tothe intake side of the blower for recirculation through the system, andmeans for discharging into the system across the sides of the table acurrent of make up air, and a dust trap through which the air passes onits return to the blower.

7. In an air cleaningsystem, a pneumatic stratifying table, a bloweradapted'to discharge air under pressure therethrough, a

dust separator and means for conducting'to Signed at Chicago, county ofCook and State of Illinois, this 20th day of May, 1927.

RAY W. ARMS.

